This creates the DynamicDirectory instance, so this is the main purpose of this class.
Sets the factory for the sub directory level.
The returned value can be used to set the factory for the sub sub directory level.
Sets the factory for the sub directory level as a function instead of an IDirectory.
This is a convenience function for cases where you do not have an IDirectory implementation. Usually this is used at the innermost level of the cached directories.
The drawback is, that chaining directories doesn't work after this call.
A directory factory is used to create instances of directories when they are needed.
In this case it is hierarchical because we can specify factory functions for several levels of a hierarchy.
In order to spawn a new directory instance, use the createDirectory call.